IS25F011A 데이터 시트보기 (PDF) - Integrated Silicon Solution

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IS25F011A

1M-BIT, 2M-BIT, AND 4M-BIT SERIAL FLASH MEMORIES WITH 4-PIN SPI INTERFACE

Integrated Silicon Solution 

IS25F011A

IS25F021A

IS25F041A

ISSI ®

Serial SRAM and Program Buffer

One of the most powerful features of the IS25F011A,

IS25F021A, and IS25F041A is the integrated Serial

SRAM and its associated Program Buffer. Together, the

264-byte Serial SRAM and 264-byte Program Buffer

provide up to 528-bytes of usable SRAM storage. The

SRAM can be used in conjunction with the Flash memory

or independently.

The main purpose of the Serial SRAM is to serve as the

primary buffer for sector data to be written into the Serial

Flash memory array. Using the Write to Sector command,

data is first shifted into the SRAM from the SPI bus. When

the command sequence has been completed, the entire

264-bytes is transferred to the Program Buffer. The Pro-

gram Buffer supports the array during the Erase/Write cycle

(tWP), freeing the SRAM to accept new data. This double-

buffering scheme increases erase/write transfer rates and

1 can eliminate the need for external RAM buffers (Figure 5).

The SRAM is fully byte-addressable. Thus, the entire

264-bytes, a single byte, or a sequence of bytes can be

2 read from, or written to the SRAM. This allows the SRAM

to be used as a temporary work area for read-modify-write

operations prior to a sector write.

The Transfer Sector to SRAM command allows the con-

3 tents of a specified sector of Flash memory to be moved to

the SRAM. This can be useful when only a portion of a

sector needs to be altered. In this case the sector is first

transferred to the SRAM, where modifications are made

4 using the Write to SRAM command. Once complete, a

Transfer SRAM to Sector command is used to update the

sector.

5

READ FROM

DEVICE INFORMATION

SECTOR

DEVICE INFORMATION SECTOR

6

READ FROM

SECTOR

SCK

CS

SI

SO

SPI

COMMAND

AND

CONTROL

LOGIC

CONFIGURATION

REGISTER

STATUS

REGISTER

COMPARE SECTOR

TO SRAM

READ FROM

PROGRAM BUFFER

READ FROM

OR WRITE TO

SRAM

WRITE TO SECTOR

(VIA SRAM &

PROGRAM BUFFER)

SERIAL FLASH MEMORY ARRAY

512, 1024, AND 2048 BYTE-ADDRESSABLE

SECTORS OF 264-BYTES EACH

TRANSFER

SECTOR TO

SRAM

TRANSFER SRAM TO SECTOR

(VIA PROGRAM BUFFER)

TRANSFER SRAM TO

PROGRAM BUFFER

PROGRAM BUFFER

SERIAL SRAM

Note:

1. A single byte, several bytes, or all bytes of a Flash sector, the SRAM, or Program Buffer may be addressed.

2. All double lines represent implied connections or actions.

TRANSFER PROGRAM

BUFFER TO SRAM

7

8

9

10

11

12

Figure 5. Command Relationships of the SPI Interface, Serial Flash Memory Array, SRAM, and Program Buffer

Integrated Silicon Solution, Inc.

5

PRELIMINARY SF001-1A

06/24/98

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